. The algae. Algae. reproduction; evolution 323 Apophloea in New Zealand waters represent examples of a reduced life cycle, because in these plants the gametophyte generation is wholly suppressed, whereas in other examples it is the sporophyte generation that has been reduced. Recently Feldmann (1952) has argued that in all three classes the primitive Ufe cycle is that with alternation of two isomorphic generations. The arguments against this have been put forward in the case of the Chlorophyceae and the thesis has been supported in the case of the Phaeophyceae. In the case of the Rhodophyceae
. The algae. Algae. reproduction; evolution 323 Apophloea in New Zealand waters represent examples of a reduced life cycle, because in these plants the gametophyte generation is wholly suppressed, whereas in other examples it is the sporophyte generation that has been reduced. Recently Feldmann (1952) has argued that in all three classes the primitive Ufe cycle is that with alternation of two isomorphic generations. The arguments against this have been put forward in the case of the Chlorophyceae and the thesis has been supported in the case of the Phaeophyceae. In the case of the Rhodophyceae it would seem that if an origin from either the Myxophyceae, uni- cellular organisms or Prasiola is envisaged, the logical, primitive Rhodophycean life cycle would consist of wholly haploid indivi- duals into which sooner or later a sporophyte would be intercalated. Feldmann's proposed primitive life cycle for the Rhodophyceae would appear unnecessarily complex and not fulfilled by any hving representatives. Fundamentally he envisages a steady reduction series throughout the class (Fig. 190). The phylogenetic history of the Chlorophyceae and Rhodo- phyceae appears to follow parallel lines if the arguments presented above are accepted. In both, the life cycle with only haploid indivi- duals is the primitive one and a diploid generation is subsequendy interpolated. In the Chlorophyceae the haploid generation even- tually disappears ( Siphonales, Valoniaceae) whereas in the Rhodophyceae it is the newly intercalated sporophytic generation that may become reduced {Phyllophora brodiaei, Ahnfeldtia plicata) as well as the gametophyte generation ( Lomentaria rosea in European waters (cf. p. 248), Hildenbrandtia and Apophloea). The phylogeny of the Phaeophyceae also fits into the general pattern if it is accepted that the primitive condition there is alternation of two isomorphic Please note that these images are extracted from scanned page images that may have be
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